The invention relates to the field of radiopharmaceuticals and describes new chelating agents as well as their tricarbonyl complexes with technetium and rhenium.
Complexes with radioactive metals have already been used for a very long time in radiodiagnosis and radiotherapy. The radionuclide technetium-99m is used most frequently, since it is especially well suited for in-vivo use because of its advantageous physical properties (no corpuscular radiation, short half-life of 6.02 h, good detectability by its 140 KeV xcex3-radiation), its short biological half-life and its broad availability. For synthesis of technetium-99m-complexes, pertechnetate is first obtained from a nuclide generator and converted by using suitable reducing agents (e.g., SnCl2) into a lower oxidation stage, which then is stabilized by a suitable chelating agent. Since technetium can be present in a number of oxidation stages (+7 to xe2x88x921), which can greatly alter the pharmacological properties by altering the charge of a complex, it is necessary to provide chelating agents or complex ligands for technetium-99m, which can bind technetium in a more secure, tight and stable manner in a defined oxidation stage. The chelating agents inhibit redox processes or technetium-release reactions that occur in vivo. Such undesirable reactions make a reliable diagnosis of diseases more difficult, since the build-up of the radiopharmaceutical agent is determined in lesions, while the pharmacokinetics of the radiopharmaceutical agent and its excretion are determined by its metabolites.
For example, cyclic amines are regarded as suitable complexing agents for technetium and rhenium isotopes [Troutner, D. E. et al., J. Nucl. Med. 21, 443 (1980)], but said amines have the drawback that they are able to bind technetium-99m in good yields only starting from a pH greater than 9. N2O2 systems [Pillai, M. R. A., Troutner, D. E. et al., Inorg. Chem. 29, 1850 (1990)] are undergoing clinical use. Non-cyclic N4-systems, such as, e.g., the HMPAO, have only a low complex stability. Tc-99m-HMPAO, because of its instability [Ballinger, J. R. et al., Appl. Radiat. Isot. 42, 315 (1991); Billinghurst, M. W. et al., Appl. Radiat. Isot. 42, 607 (1991)], must be administered immediately after its labeling, so that the proportion of decomposition products that have a pharmacokinetics and excretion other than the diagnostic agent can be kept small. The radiochemical contaminants impede the detection of the diseases that are to be diagnosed. N2S2 chelating agents [Bormans, G. et al., Nucl. Med. Biol. 17, 499 (1990)], such as, e.g., ethylene dicysteine [Verbruggen, A. M. et al., J. Nucl. Med. 33, 551 (1992)] comply, with the requirement for adequate stability of the corresponding technetium-99m complex, but radiodiagnostic agents with a purity above 69% form only starting from a pH greater than 9. N3S systems (Fritzberg, A., EPA 0 173 424 and EPA 0 250 013) form stable technetium-99m complexes, but must be heated to temperatures of about 100xc2x0 C. to incorporate the radioisotope. Another drawback of the N2S2 and N3S systems consists in that the latter are partially excreted quickly and without specific build-up of the organism, so that the latter are used clinically only as renal functional diagnostic agents. They therefore have only a limited suitability. The coupling of such chelates or chelating agents to substances that accumulate selectively in foci of disease cannot be triggered with simple agents, so that the latter are generally distributed non-specifically in the organism.
In recent years, the demand for radiodiagnostic agents and radiotherapeutic agents that accumulate specifically in diseased tissues has increased. This can be achieved if complexing agents can be coupled easily to substances that accumulate selectively in lesions and in this process do not lose their advantageous complexing properties. Since a weakening of the complex stability is observed frequently after a complexing agent is coupled to such a molecule, the previous attempts to couple chelating agents to selectively accumulating substances do not appear to be very satisfactory. The reason lies in the fact that a diagnostically intolerable proportion of the isotope is released from the conjugate in vivo [Brechbiel, M. W. et al., Inorg. Chem. 25, 2772 (1986)]. It is therefore necessary to provide bifunctional complexing agents that carry both functional groups for stable binding of the desired metal ion and one or more other functional groups for binding the selectively accumulating molecule. Such bifunctional ligands make possible a specific, chemically defined binding of technetium or rhenium isotopes to the most varied biological materials even if a so-called prelabeling is performed. Some chelating agents were described that were coupled to, e.g., monoclonal antibodies (e.g., EP 247 866 and EP 188 256) or fatty acids (EP 200 492). As chelating agents, however, the already mentioned N2S2 systems were used, which were not very suitable because of their poor stability. Since both the properties of the selectively accumulating substances and the mechanisms according to which they are concentrated in lesions are very different, it is also necessary to vary the chelating agents that can be coupled and to be able to adapt the physiological requirements of the coupling partner with respect to its lipophilia and hydrophilia, membrane permeability or impermeability.
To deal with the above-mentioned drawbacks and limitations of the established chelating groups as well as their conjugates with biomolecules, which accumulate selectively in diseased tissues, it has been attempted in recent years to use tricarbonyl-technetium-I compounds and tricarbonyl-rhenium-I compounds for labeling such biomolecules (Lit. R. Alberto et al., Achievements and Prospects of New Radiotracers, 1997, C3, p. 57 (Abstracts)). Since, however, tricarbonyl-technetium-I-triaqua ions and tricarbonyl-rhenium-I-triaqua ions with high stability are bonded non-specifically and quickly by serum proteins, however, it has not yet been possible to synthesize adequately stable conjugates between substances that accumulate selectively in diseased tissues with tricarbonyl-technetium-I complexes and tricarbonyl-rhenium-I complexes.
International Patent Application WO 98/48848 describes a general method for the production of tricarbonyl-technetium-I complexes and tricarbonyl-rhenium-I complexes. Special chelating agents, which can be coupled to biomolecules and with whose aid especially stable complexes are obtained, are not mentioned in this application.
The object of this invention was therefore to develop stable tricarbonyl-technetium-I complexes and tricarbonyl-rhenium-I complexes that can be coupled to various compounds that selectively accumulate in diseased tissues. Another object of the invention was to provide such chelating agents or complexes that can be coupled and that have a large chemical range of variation of the substituents so as to be able to adapt the latter to the above-referenced requirements. Another aspect of the invention relates to processes for the production of the compounds as well as the pharmaceutical agents that contain the compounds.
This object is achieved by the compounds of general formula (I)
Yxe2x80x94CR1R2xe2x80x94(CR3R4)nxe2x80x94N (CR5R6xe2x80x94COOR7)xe2x80x94CR8R9xe2x80x94COxe2x80x94Xxe2x80x83xe2x80x83(I)
in which
n stands for numbers 0, 1 or 2;
R1, R2, R3, R4, R5, R6, R8 and R9 are the same or different and in each case represent a hydrogen atom or an unbranched, branched, cyclic or polycyclic C1-C60 alkyl, C1-C60 alkenyl, C5-C60 polyalkenyl, C1-C60 alkinyl; C5-C60 polyalkinyl, C5-C60 aryl, C5-C60 alkylaryl or C5-C60 arylalkyl radical, which optionally is substituted with hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 20 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series O, N, S, P, As, Se;
R7 stands for a hydrogen atom or an alkali cation or an alkaline-earth cation or a primary, secondary or tertiary ammonium ion;
x represents a radical Oxe2x80x94R7 or means a radical NR10R11, in which R10 and R11 are the same or different and in each case represent a hydrogen atom or an unbranched, branched, cyclic or polycyclic C1-C60 alkyl, C1-C60 alkenyl, C5-C60 polyalkenyl, C1-C60 alkinyl, C5-C60 polyalkinyl, C5-C60 aryl, C5-C60 alkylaryl or C5-C60 arylalkyl radical, which optionally is substituted with hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 20 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series O, N, S, P, As, Se; or R10 and/or R11 are the same or different and in each case represent a hydrogen atom, a peptide radical, protein radical, a modified or unmodified DNA or RNA oligonucleotide radical, a modified or unmodified aptamer radical or a PNA radical;
Y stands for an R12xe2x80x94S radical, in-which R12 represents a hydrogen atom or an unbranched, branched, cyclic or polycyclic C1-C60 alkyl, C1-C60 alkenyl, C5-C60 polyalkenyl, C1-C60 alkinyl, C5-C60 polyalkinyl, C5-C60 aryl, C5-C60 alkylaryl or C5-C60 arylalkyl radical, which optionally is substituted with hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 20 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series O, N, S, P, As, Se; or R12 represents a peptide radical, protein radical, a modified or unmodified DNA or RNA-oligonucleotide radical, a modified or unmodified aptamer radical or a PNA radical;
or Y stands for an R13R14P radical, in which R13 and R14 are the same or different and in each case represent a hydrogen atom or an unbranched, branched, cyclic or polycyclic C1-C60 alkyl, C1-C60 alkenyl, C5-C60 polyalkenyl, C1-C60 alkinyl, C5-C60 polyalkinyl, C5-C60 aryl, C5-C60 alkylaryl radical or C5-C60 arylalkyl radical, which optionally is substituted with hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 20 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series O, N, S, P, As, Se;
or Y stands for a monocyclic or polycyclic heteroaromatic compound, which contains at least one heteroatom from the series O, S, N and/or P; and their complexes with tricarbonyl-technetium-I radicals or tricarbonyl-rhenium-I radicals of the corresponding radioisotopes.
Preferred are those compounds in which radicals R1, R2, R3, R4, R5, R6, R8 and R9 in each case represent a hydrogen atom. Those compounds are also preferred in which R7 stands for a hydrogen atom or an alkali cation or an alkaline-earth cation.
Radical Y preferably stands for a monocyclic heteroaromatic compound or a radical R12xe2x80x94S, in which R12 preferably stands for an unbranched, branched, cyclic or polycyclic, saturated or unsaturated C1-C60 alkyl radical. Especially preferred are those compounds in which radical R12 represents a C1-C10 alkyl chain.
Radical X preferably stands for a group Oxe2x80x94R7, in which R7 stands for a hydrogen atom or an alkali cation or an alkaline-earth cation or a primary, secondary or tertiary ammonium ion. Radical X also preferably stands for a group NR10R11, in which R10 and R11 are the same or different and in each case represent a hydrogen atom, a peptide radical, protein radical, a modified or unmodified DNA or RNA-oligonucleotide radical, a modified or unmodified aptamer radical or a PNA radical, or for a group NR10R11 in which R10 and R11 are the same or different and in each case stand for a hydrogen atom, an unbranched, branched, cyclic or polycyclic, saturated or unsaturated C1-C60 alkyl radical.
The production of the compounds of general formula (I) according to the invention is carried out in that compounds of general formula (II) are reacted with compounds of general formula (III) according to the reaction diagram below: 
in which
R1, R2, R3, R4, R5, R6, R7, R8 and R9 have the above-indicated meaning, and H in HX stands for a proton.
The production of the technetium-99m complexes or Re-tricarbonyl complexes according to the invention is carried out by reaction of the previously synthesized technetiumtricarbonyl precursors or rhenium tricarbonyl precursors [R. Alberto et al., Achievements and Prospects of New Radiotracers, 1997, C3, p. 57 (Abstracts)] with the tridentates according to the invention.
Other objects of the invention are compounds of general formula (IV)
Yxe2x80x94CR1R2xe2x80x94(CR3R4)nxe2x80x94N [(CR5R6)2xe2x80x94Z]xe2x80x94CR8R9xe2x80x94COxe2x80x94Xxe2x80x83xe2x80x83(IV)
in which
n stands for numbers 0, 1 or 2;
R1, R2, R3, R4, R5, R6, R8 and R9 are the same or different and in each case represent a hydrogen atom or an unbranched, branched, cyclic or polycyclic C1-C60 alkyl, C1-C60 alkenyl, C5-C60 polyalkenyl, C1-C60 alkinyl, C5-C60 polyalkinyl, C5-C60 aryl, C5-C60 alkylaryl or C5-C60 arylalkyl radical, which optionally is substituted with hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 20 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series O, N, S, P, As, Se;
X represents a radical Oxe2x80x94R7 or means a radical NR10R11, in which R10 and R11 are the same or different and in each case represent a hydrogen atom or an unbranched, branched, cyclic or polycyclic C1-C60 alkyl, C1-C60 alkenyl, C1-C60 polyalkenyl, C1-C60 alkinyl, C5-C60 polyalkinyl, C5-C60 aryl, C5-C60 alkylaryl or C5-C60 arylalkyl radical, which optionally is substituted with hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 20 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series O, N, S, P, As, Se; or R10 and/or R11 are the same or different and in each case represent a hydrogen atom, a peptide radical, protein radical, a modified or unmodified DNA or RNA-oligonucleotide radical, a modified or unmodified aptamer radical or a PNA radical;
Y stands for an R12xe2x80x94S radical, in which R12 represents a hydrogen atom or an unbranched, branched, cyclic or polycyclic C1-C60 alkyl, C1-C60 alkenyl, C5-C60 polyalkenyl, C1-C60 alkinyl, C5-C60 polyalkinyl, C5-C60 aryl, C5-C60 alkylaryl or C5-C60 arylalkyl radical, which optionally is substituted with hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 20 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series O, N, S, P, As, Se; or R12 represents a peptide radical, protein radical, a modified or unmodified DNA or RNA oligonucleotide radical, a modified or unmodified aptamer radical or a PNA radical;
or Y stands for an R13R14P radical, in which R13 and R14 are the same or different and in each case represent a hydrogen atom or an unbranched, branched, cyclic or polycyclic C1-C60 alkyl, C1-C60 alkenyl, C5-C60 polyalkenyl, C1-C60 alkinyl, C5-C60 polyalkinyl, C5-C60 aryl, C5-C60 alkylaryl or C5-C60 arylalkyl radical, which optionally is substituted with hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 20 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series O, N, S, P, As, Se;
or Y stands for a monocyclic or polycyclic heteroaromatic compound that contains at least one heteroatom from the series O, S, N and/or P;
Z stands for an R12xe2x80x94S radical, in which R12 represents a hydrogen atom or an unbranched, branched, cyclic or polycyclic C1-C60 alkyl, C1-C60 alkenyl, C5-C60 polyalkenyl, C1-C60 alkinyl, C5-C60 polyalkinyl, C5-C60 aryl, C5-C60 alkylaryl or C5-C60 arylalkyl radical, which optionally is substituted with hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 20 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series O, N, S, P, As, Se;
or Z stands for an R13R14P radical, in which R13 and R14 are the same or different and in each case represent a hydrogen atom or an unbranched, branched, cyclic or polycyclic C1-C60 alkyl, C1-C60 alkenyl, C5-C60 polyalkenyl, C1-C60 alkinyl, C5-C60 polyalkinyl, C5-C60 aryl, C5-C60 alkylaryl or C5-C60 arylalkyl radical, which optionally is substituted with hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 20 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series O, N, S, P, As, Se;
or Z stands for a monocyclic or polycyclic heteroaromatic compound, which contains at least one heteroatom from the series O, S, N and/or P;
as well as their complexes with tricarbonyl-technetium-I radicals or tricarbonyl-rhenium-I radicals of the corresponding radioisotopes.
Preferred are those compounds in which radicals R1, R2, R3, R4, R5, R6, R8 and R9 in each case represent a hydrogen atom. Radical Y preferably stands for a radical R12xe2x80x94S, in which R12 preferably stands for an unbranched, branched, cyclic or polycyclic, saturated or unsaturated C1-C60 alkyl radical. Especially preferred are those compounds in which radical R12 represents a C1-C10 alkyl chain.
Radical X preferably stands for a group Oxe2x80x94R7, in which R7 stands for a hydrogen atom or an alkali cation or an alkaline-earth cation or a primary, secondary, or tertiary ammonium ion. In addition, radical X preferably stands for a group NR10R11, in which R10 and R11 are the same or different and in each case represent a hydrogen atom, a peptide radical, protein radical, a modified or unmodified DNA or RNA-oligonucleotide radical, a modified or unmodified aptamer radical or a PNA radical, or for a group NR10R11, in which R10 and R11 are the same or different and in each case stand for a hydrogen atom, an unbranched, branched, cyclic or polycyclic, saturated or unsaturated C1-C60 alkyl radical.
Radical Z preferably stands for an R12xe2x80x94S radical, in which R12 preferably represents a C1-C10 alkyl chain.
The production of the compounds of general formula (IV) according to the invention is carried out in that compounds of general formula (V) are reacted with compounds of general formula (III) according to the reaction diagram below: 
in which
R1, R2, R3, R4, R5, R6, R7, R8 and R9 have the meaning that is indicated above, Xxe2x80x2 stands for a leaving group, such as, e.g., a halogen atom, and H in HX stands for a proton.
The production of the technetium-99m- or Re-tricarbonyl complexes according to the invention is carried out by reaction of the previously synthesized technetiumtricarbonyl precursors or rheniumtricarbonyl precursors [R. Alberto et al., Achievements and Prospects of New Radiotracers, 1997, C3, p. 57 (Abstracts)] with the tridentates according to the invention.
Other objects of the invention are radiopharmaceutical compositions for non-invasive in-vivo visualization of receptors and receptor-containing tissues, which contain a compound of general formula (I) or a compound of general formula (IV) as well as additives that are optionally commonly used in galenicals. The radiopharmaceutical composition is administered to a patient in an amount of 0.1 mCi to 1 Ci, preferably 1 mCi to 500 mCi per 70 kg of body weight. The radiation that is given off by the patient is recorded with a gamma-camera.
Surprisingly enough, the chelates that are synthesized and labeled with Tc-99m tricarbonyl or Re-tricarbonyl showed a higher stability than comparable N3S and N2S2 systems, which were described in the literature. Thus, e.g., in a substance according to the invention (Example 2b), no decomposition products were observed after 26 hours of incubation in serum. The complexes are stable, so that at room temperature, no exchange of chelating agents for histidine is carried out. The. chelates and tricarbonyl-Tc-99m and Re-tricarbonyl complexes that are described in this invention are thus clearly better suited for diagnostic and therapeutic purposes than the previously known systems. A special advantage of the compounds according to the invention consists in the fact that their syntheses can be directed without using sulfur protective groups. This makes their synthesis very simple, and in addition, such compounds that are described according to the invention in particular offer the advantage that after radiochemical labeling, no further foreign molecules are contained in the solutions that are to be administered intravenously for radiodiagnosis or radiotherapy. Such foreign molecules frequently disrupt the biodistribution of the radiopharmaceutical agent and can adversely affect the diagnostic information content of the SPECT imaging. In addition, the labelings on such ligands or their coupling products can be performed on substances that accumulate selectively on diseased tissues under very mild conditions. The labeling of the ligands according to the invention or the coupling products on substances that accumulate selectively in diseased tissues is possible at room temperature and at physiologic pH, without the protective groups first being cleaved under the action of bases, acids or other adjuvants that are known to one skilled in the art. This ensures that the frequently very sensitive substances that accumulate selectively in diseased tissues are not chemically altered by such adjuvants, which frequently reduces their selective accumulation in the diseased tissue and thus would adversely affect the information content of the SPECT images.
The coupling to substances that accumulate selectively in diseased tissues is carried out according to the methods that are known to one skilled in the art [e.g., Fritzberg et al.; J. Nucl. Med. 26, 7 (1987)], for example by reaction of electrophilic groups of the complex ligand according to the invention with nucleophilic centers of the substances that accumulate selectively in diseased tissues. Otherwise, nucleophilic groups of the chelating agent are coupled with electrophilic groups of the substances that accumulate selectively in diseased tissues.
As coupling partners, i.a., various biomolecules are provided as well as biological ligands, which bind to specific receptors and thus can be detected in tissue whose receptor density is altered. These include, e.g., modified or unmodified peptides, unmodified or modified proteins, steroid hormones or derivatives thereof, growth factors, neutrotransmitters, modified DNA or RNA oligonucleotides and modified or unmodified aptamers or PNA molecules.
The production of the pharmaceutical agents according to the invention is carried out in a way that is known in the art, by the complexing agents according to the invention being dissolved in aqueous medium optionally with the addition of the additives that are commonly used in galenicals and then sterilized by filtration. Suitable additives are, for example, physiologically harmless buffers, additions of electrolytes (e.g., sodium chloride) and optionally stabilizers. The pharmaceutical agent according to the invention is present in the form of a solution or in freeze-dried form and is mixed shortly before administration with a solution of a Tc-99m tricarbonyl precursor or Re-tricarbonyl precursor.
In the nuclear-medicine in-vivo use, the agents according to the invention are injected intravenously, intraarterially, peritoneally or intratumorally.
The examples below are used for a more detailed explanation of the subject of the invention.